#! /bin/bash

input_dir="$1"
output_dir="$2"

case "$output_dir" in
    '') output_dir="$input_dir/auto-organized"
esac

find "$input_dir" -type f -iregex '^.+\.jp[e]*g$' | while read -r path; do
    # TODO Use "exiftool" instead of "file". Unclear which timestamp field to use.
    file_data=$(file "$path")
    if echo "$file_data" | grep 'image data' > /dev/null; then
        read -r year0 month0 day0 hour0 minute0 second0 < <(
            echo "$file_data" \
            | grep -o 'Exif Standard: \[.*\]' \
            | grep -oE 'datetime=[0-9]{4}:[0-9]{2}:[0-9]{2} +[0-9]{2}:[0-9]{2}:[0-9]{2}' \
            | sed 's/^datetime=//' \
            | sed 's/:/ /g'
        )
        if ! [[ "$year0" = '' && "$month0" = '' && "$day0" = '' && \
                "$year0" -eq 0 && "$month0" -eq 0 && "$day0" -eq 0 ]]
        then
            # Force base 10, since leading zeros may cause an assumption of base 8:
            year=$((  10#${year0}  ))
            month=$(( 10#${month0} ))
            day=$((   10#${day0}   ))
            hour=$((  10#${hour0}  ))
            minute=$((10#${minute0}))
            second=$((10#${second0}))

            digest=$(sha256sum "$path" | awk '{print $1}')
            suffix=$(echo "$path" | awk -F . '{print tolower($NF)}')
            new_dir="${output_dir}/${year}/${month}/${day}"
            new_name="${year}-${month}-${day}--${hour}-${minute}-${second}--${digest}.${suffix}"
            new_path="$new_dir/$new_name"

            printf 'old: %s\n' "$path"
            printf 'new: %s\n' "$new_path"
            printf '\n'
        fi
    fi
done